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    SubjectRe: [PATCH v4 63/66] i915: Use the VMA iterator
    On Thu, Jan 20, 2022 at 03:59:11PM +0100, Vlastimil Babka wrote:
    > On 12/1/21 15:30, Liam Howlett wrote:
    > > From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
    > >
    > > Replace the O(n.log(n)) loop with an O(n) loop.
    >
    > Not true?

    Oh, right, that should have been just the linked-list walk.
    I misread it as calling find_vma() for each iteration instead
    of just the first one. Liam, do you mind updating the changelog
    here?

    I wonder whether we want a "for_each_contiguous_vma()" that
    will stop on a hole. It seems like a relatively sensible thing
    to do -- walk across a contiguous range of memory and stop if
    there's no VMA mapping a page. Like gup(), for example.

    > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
    > > Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
    >
    > Acked-by: Vlastimil Babka <vbabka@suse.cz>
    >
    > > ---
    > > drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 14 +++++---------
    > > 1 file changed, 5 insertions(+), 9 deletions(-)
    > >
    > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
    > > index 3173c9f9a040..39960973c130 100644
    > > --- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
    > > +++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
    > > @@ -425,12 +425,11 @@ static const struct drm_i915_gem_object_ops i915_gem_userptr_ops = {
    > > static int
    > > probe_range(struct mm_struct *mm, unsigned long addr, unsigned long len)
    > > {
    > > - const unsigned long end = addr + len;
    > > + VMA_ITERATOR(vmi, mm, addr);
    > > struct vm_area_struct *vma;
    > > - int ret = -EFAULT;
    > >
    > > mmap_read_lock(mm);
    > > - for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) {
    > > + for_each_vma_range(vmi, vma, addr + len) {
    > > /* Check for holes, note that we also update the addr below */
    > > if (vma->vm_start > addr)
    > > break;
    > > @@ -438,16 +437,13 @@ probe_range(struct mm_struct *mm, unsigned long addr, unsigned long len)
    > > if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
    > > break;
    > >
    > > - if (vma->vm_end >= end) {
    > > - ret = 0;
    > > - break;
    > > - }
    > > -
    > > addr = vma->vm_end;
    > > }
    > > mmap_read_unlock(mm);
    > >
    > > - return ret;
    > > + if (vma)
    > > + return -EFAULT;
    > > + return 0;
    > > }
    > >
    > > /*
    >

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